1. Field of the Invention
The present invention relates to an one-way communication method, a mobile station apparatus, a wireless base station apparatus. More particularly, the present invention relates to an one-way communication method for transmitting communication data in one direction from the mobile station apparatus to the wireless base station apparatus, and relates to the mobile station apparatus and the wireless base station apparatus used for carrying out the one-way communication method. By the way, in the following descriptions, the mobile station apparatus and the wireless base station apparatus are simply referred to as a mobile station and a base station.
2. Description of the Related Art
In a general cellular system, relationship between the base station and the mobile station with respect to communication control is a master/slave relationship. Therefore, it is general that the base station collectively manages transmission resource assignment so that the mobile station transmits communication data using the transmission resource reported from the base station. Examples of the transmission resource assignment are assignment of spreading code in a CDMA (Code Division Multiple Access) scheme, assignment sub-channels in OFDM (Orthogonal Frequency Division Multiplexing)/OFDMA (Orthogonal Frequency Division Multiple Access) schemes, and assignment of time-division slots in a TDMA (Time Division Multiple Access) scheme.
As a prior art document, Japanese Laid-Open Patent application No. 11-27231 (document 1) discloses a wireless communication system in which a base station and a mobile station are connected by OFDM. In the system, when the base station receives an access request from the mobile station, the base station assigns, to the mobile station, some sub-carriers from all sub-carries that can be assigned to the mobile station according to the amount of information communicated by the mobile station.
Japanese Laid-Open Patent Application No. 2001-103032 (document 2) discloses an OFDM modulation/demodulation circuit for processing an OFDM signal used in digital wireless communications. The OFDM modulation/demodulation circuit changes a transmission signal modulation scheme, a symbol rate, a ratio of error correction coding and the like according to transmission route environment in order to maximize a transmission speed.
Japanese Laid-Open Patent Application No. 2005-198215 (document 3) discloses a wireless communication system for performing transmission by the OFDM scheme using a plurality of sub-carriers orthogonal with each other in which a wireless transmission apparatus transmits a preamble signal before transmitting data signals.
Since the relationship between the base station and the mobile station is the master/slave relationship in the conventional wireless system, the mobile station requests the base station to assign transmission resources so as to send communication data via the base station using the wireless resources assigned based on the instruction of the base station when the mobile station sends one-way communication data to the base station and even when the mobile station sends data to another mobile station near the mobile station.
Thus, even when there is no downlink communication data from the base station to the mobile station, the base station should send a connection control signal using a broadcast signal and the like. In addition, even for communication data to be transmitted between closely located mobile stations, it is necessary to send and receive a resource assignment request and a resource assignment report via the base station. Thus, in terms of effective use of transmission resources such as transmission frequencies, the conventional wireless system is inefficient in which resources are used uselessly.